Controlling a power switching apparatus such as a breaker to automatically close a circuit within a short time interval of, for example, one second subsequently to circuit opening operation is called “a high-speed reclose”. For example, in the case of a power transmission line accident that is mostly a flashover accident of an insulator by a thunderbolt, a secondary arc current attributed to the accident automatically disappears if the fault section is once separated from the power source by opening the circuit of the breaker between the power source and a power transmission line. Therefore, any accident does not occur again if a breaker circuit is closed by performing high-speed reclose, and the operation can be performed without abnormality. In this case, it is required to appropriately control a pole-close timing of the breaker in order to suppress generation of transit voltage and current at the timing of turning on the breaker at a reclose timing.
For example, the power switching control apparatus described in a Patent Document 1 makes a functional approximation of the measured waveforms of a power source side voltage of the breaker and the load side voltage of the breaker and estimates the interpolar voltage at and after the current time by using an approximation function. Then, the estimated interpolar voltage is corrected based on a pre-arc characteristic of the breaker and the mechanical operation variation characteristic of the breaker, the target pole-close timing is determined by using the corrected interpolar voltage, and the breaker pole is closed at the determined target pole-close timing.
In the Patent Document 1, there is no description about the determining method of the target pole-close timing of each phase when the three-phase breaker is sequentially turned on every phase. However, when the breaker between the power source and the three-phase balanced transmission line is sequentially closed respective phases, there is a possibility that load side voltages of the second and third turn-on phases are varied by receiving the influence of turning on the preceding turn-on phase (hereinafter, referred to as a preceding turn-on phase). For this reason, if the target pole-close timings of the second and third turn-on phases are determined, respectively, by using the interpolar voltages of the second and third turn-on phases estimated immediately after current interruption by closing the circuit of the breaker and the second and third turn-on phases are closed at the target pole-close timings, the transit voltage and current at the timing of turning on the breaker cannot be suppressed.
In order to solve this problem, the power switching control apparatus described in a Patent Document 2 delays a pole-close possible timing that is the start timing of the pole-close timing domain by a predetermined delay time interval with estimation of a fluctuation in the breaker interpolar voltage due to the turning-on of the preceding turn-on phase when calculating the pole-close timing domain of the subsequent turn-on phases after the second turn-on phase. Moreover, the power switching control apparatus described in the Patent Document 2 applies a breaker interpolar voltage maximum fluctuation value which is previously set with estimation of the fluctuation in the breaker interpolar voltage due to the turning-on of the preceding turn-on phase when estimating the breaker interpolar voltage of the subsequent turn-on phase.